The invention relates generally to a showerhead apparatus for radical-assisted deposition in chemical vapor deposition equipment for performing a semiconductor manufacturing process. More particularly, the present invention relates to a showerhead apparatus for radical-assisted deposition in which a showerhead is consisted of a two-stair structure to generate plasma, so that uniformity of a thin film can be improved, the deposition efficiency can be increased and generation of particles is minimized when a thin film is deposited on a large-caliber wafer or a substrate.
Generally, in a process of manufacturing a semiconductor, the chemical vapor deposition apparatus for depositing a thin film on a wafer or a substrate employs a plasma in order to deposit a thin film of a high quality at low temperature, whereby a raw material is activated to deposit a thin film on the wafer or the substrate. A conventional apparatus for generating plasmas will be now explained in short by reference to FIG. 1a. 
FIG. 1a is a schematic view illustrating an entire structure of a conventional plasma chemical vapor deposition apparatus. The apparatus includes chamber 107 below which an exhaust outlet 106 is formed, a gas injection tube 102 formed through the upper center of the chamber 107 for injecting a plasma generating gas, a showerhead 110 having a plurality of holes, for spraying the plasma generating gas induced from the gas injection tube 102, which is surrounded by a shield 104 and is also mounted under the gas injection tube 102, a shower ring 103 mounted below the showerhead 110 for spraying a raw material gas supplied from a raw material gas injection tube 101 when a plasma is used, a substrate 108 on which a thin film is deposited the gas sprayed from the shower ring 103 and a heater 109 supporting the substrate 108 for providing a given thermal source to the substrate.
At this time, an insulating plate 105 having an electrode plate for generating a plasma by an outside RF power supply (not shown) is formed on the chamber 107 at the portion of which the gas injection tube 102 passes through. Also, the shower ring 103 is separated from the plasma generating apparatus.
In the above conventional structure, it is impossible to accurately adjust the raw material gas since the shower ring 103 is directly exposed to the plasma generating gas passing through the showerhead 110 due to the temperature elevated by the plasma. This results in degrading the quality of a thin film to be grown. Also, in case of employing a large-caliber wafer, as it is difficult to uniformly spray a raw material gas on the entire surface of the wafer, forming a uniform thin film is made impossible. Further, as the distance between the shower ring and the wafer or the shower ring and the substrate is distant, there is a problem that the deposition efficiency of the raw material gas is degraded.
In order to overcome the above problems, Korean Patent Application No. 99-0243446 proposes a showerhead apparatus including a plasma generating section, which includes a showerhead of a two-stair structure the upper and lower portion of which has a buffer, respectively, whereby the raw material gas sprayed into the plasma can be constantly distributed to form a uniform thin film on a wafer or a substrate.
FIG. 1b is a schematic view of the showerhead apparatus including the above plasma generating section. The showerhead apparatus includes first and second showerheads 201 and 202 having a two-stair structure, the upper and lower portion of which has buffers 201a and 202a, respectively. Here, the showerhead is constructed wherein a plasma is generated by the first upper buffer 201a of the first showerhead 201, the plasma is sprayed on a wafer 203 through a plasma spray hole 201b passing through the second buffer 202a, a raw material gas is injected into the second buffer 202a of the second showerhead 202 and the raw material gas is sprayed through a plurality of raw material gas spray holes 202b formed at the below plate of the second buffer 202a. In the above conventional showerhead apparatus, however, the generated plasma is introduced into the chamber through the plasma spray holes passing through the second buffer, so that the probability or the number in which particles constituting plasmas such as positive ions, electrons, radical etc. collide each other within the spray hole or collide against the internal wall of the spray hole is increased. Thus, there is a drawback that the plasma efficiency is decreased due to loss of the energy. In addition, as the raw material gas introduced into the second buffer is caused to spiral heavily within the second buffer by the plurality of plasma spray holes formed at the second buffer, there are problems that the internal of the showerhead is contaminated and a lot of particles are generated.
The present invention is contrived to solve the above problems and an object of the present invention is to provide a showerhead apparatus for radical-assisted deposition including a showerhead of a two-stair structure separated by a given distance, which has a first buffer for uniformly distributing a raw material gas and a second buffer for uniformly distributing a plasma gas, wherein a plasma is generated within the showerheads and the raw material gas sprayed into the plasma is constantly maintained, thus forming a uniform thin film on a wafer or a substrate.
Also, another object of the present invention is to provide a showerhead apparatus for radical-assisted deposition capable of forming a thin film of a high quality at a low-temperature process while simplifying the structure of two-stair showerheads having a first buffer and a second buffer.
In order to accomplish the above object, the present invention provides a showerhead apparatus for radical-assisted deposition comprising a raw material gas spray means including a first buffer which is divided into upper and lower layers for uniformly distributing a gas introduced from a raw material gas injection tube, wherein a plurality of raw material gas spray holes for spraying the raw material gas distributed within the first buffer at a given flow rate is formed at a lower plate of the spray means; a plasma generating gas spray means including a second buffer for uniformly distributing a plasma generating gas between with the raw material gas spray means, wherein a plurality of plasma generating gas spray holes and through holes for spraying the plasma generating gas distributed within the second buffer are formed at a lower plate of the spray means, respectively; a guide means for communicating the raw material gas spray holes in the raw material gas spray means and the through holes in the plasma generating gas spray means and for inducing the raw material gas and the plasma generating gas so that they are not mixed; and a RF generating means mounted at one outside side of the raw material gas spray means, wherein a RF rod for applying an outside RF power is included at a lower plate of the RF generating means.